Tang was born in Wenzhou, Zhejiang, China and raised in Hangzhou, Zhejiang to Wenzhounese parents. She is the only child of a former stage actress and painter. In an interview, she explained that she often travelled around China and learned to paint, adding that she was influenced by her parents.[2] Tang graduated from a local vocational high school in her hometown in 1996, where her teachers described her as "athletic" and a "good student who always did her homework". She had no plans to become famous; she originally aspired to become an archaeologist or lawyer.[3] Tang made the decision to enter the entertainment industry after doing some modelling in 1997. She graduated from the Central Academy of Drama in 2002.

Shortly after her university graduation, Tang met Stan Lai during one of his trips to China. He was impressed by the actress, and was quoted as saying, "The number of stars may not be good actors, a lot of good actors may not be good stars, but Tang Wei was fortunate to have done it." He proceeded to recommend her to several directors and was thus cast in more roles, although she was relatively unknown outside her hometown in China at this time. Nonetheless, Tang starred in a TV series, Policewoman Swallow (2004) and a brief university drama, Che Guevara (2004). After working with a more diverse group of actresses, she also appeared in TV dramas Leaving Seafront Street (2005), East Meets West (2005) and Born in the 60s (2006).[4]

From November 2009 to March 2010, Tang filmed with Hyun Bin in Late Autumn (2010), directed by Kim Tae-yong.[12][13]Late Autumn was shot in Seattle, Washington.[14][15] In Crossing Hennessy (2010), a romantic drama, with Jacky Cheung, Tang plays the orphaned Oi Lin who falls for the troubled Xu. Her uncle proceeds to attempt to avert the attraction to another man, and succeeds as the plan ends in marriage.[16] She learned Cantonese during this time, and was reported to be very capable despite the limited filming time and her role in the movie.[17] Tang's first film to be shown in China since Lust, Caution, a March 2010 news article quoted her as saying, "Coming to Hong Kong for this premiere, I can see director Ivy and co-star Andy On again. I've been very happy. Now I'm just excited to see the movie. I will be happy if everyone can see my work."[18]

In 2011, Tang returned to mainstream cinema with two major films, Speed Angels and Dragon. Although the former was not a box office success, Dragon was a hit at the Chinese box office.

In 2013, Tang had her biggest commercial success when she starred opposite actor Wu Xiubo in the Xue Xiaolu directed romantic comedy Finding Mr. Right, which garnered her high praise from reviewers and was a runaway success at the box office. Shanghai newspaper, City Weekend wrote, "The most compelling element of the movie however, is still Tang Wei herself. It is a testament to her on-screen charisma that such a shrill, materialistic and generally awful character can have the audience rooting for her. After being temporarily banned from Chinese cinema for her controversial debut, Tang proves that she is one of the most promising young actresses the PRC has available. Let’s hope that the local filmmakers realize they have found Mrs. Right."[21]

Tang met actor Zhu Yuchen, a Shanghai native, in 1995. By 1998, the couple had moved in together while continuing university education. They officially split in 2002, a few days before graduation.[22]

Tang ended a three-year relationship with Tian Yu (田羽) in December 2007.[23] She would not reveal further details or reasons for the split, but stated, "Tian Yu is important to me, and for years, he was the person who treated me the best. He always cared about and helped me quietly. Without him, I definitely would not have played a role in Lust, Caution, and wouldn't have the success I've made today. I will always feel grateful to him." Following the success of Lust, Caution, Tang obtained residency in Hong Kong.[24]

Tang began dating South Korean film director Kim Tae-yong in 2009. The couple met while filming Late Autumn.[25][26]

On July 12, 2014, Tang and Kim married in the front yard of the home of film legend Ingmar Bergman on the remote Swedish island of Fårö;[27][28] a formal wedding ceremony was later held in Hong Kong, with only immediate family members as guests.[29][30][31] On August 27, 2016, Tang gave birth to their daughter.[32]